When replacing sway-bar links and torsion rods, etc. on the rear of a 1992 LEXUS LS400, is it better to have the vehicle on jackstands (with suspension parts hanging) or have the tires resting on a ramp? Which causes less tension as ypu remove patrs?

With everything unloaded, no weight on suspension. On some things before tightening though they need to be loaded else the rubber bushings are over stressed. You need a shop manual for it. Online at the Toyota tech site.